Optics of Surfaces and Interfaces 13

Centro de Investigaciones en Optica, Leon, Mexico

June 4, 2019 @ 5:10pm

Two-photon absorption spectroscopy and anisotropy of bulk III-V and IV semiconductors and quantum dots

Brandon J. Furey¹, Rodrigo M. Barba-Barba², Tushti Shah¹, Alan Bernal², Brian A. Korgel¹, Ramon Carriles², Bernardo S. Mendoza², Michael C. Downer¹

¹University of Texas at Austin, ²Centro de Investigaciones en Optica, A.C. Leon, Mexico

We previously reported results for the two-photon absorption (2PA) coefficient of silicon quantum dots (SiQD) at 800 nm using two-photon-induced photoluminescence (2PIP). SiQD have applications in bio-imaging due to the efficient emission of photoluminescence and non-toxicity, and excitation by 2PA enables deeper penetration depth and increased resolution. A first-principles theoretical model is under development to relate the 2PA response of bulk Si to SiQD and explain the spectral features and size dependence of 2PA in colloidal, ligand-passivated SiQD. Thus we need to understand the 2PA spectrum and anisotropy of bulk Si. The experimental procedure was tested with Gallium phosphide (GaP) since the spectral region of interest Τ 𝐸 𝑔 2 < ℏ𝜔 < 𝐸 𝑔 is in the visible. The 2PA coefficient of GaP was measured by open-aperture z-scan in the spectral range 650 – 1050 nm. Anisotropy in the polarization dependence of 2PA was measured by polarization rotation. Ongoing work using pump-probe spectroscopy to study GaP, Gallium arsenide (GaAs), bulk silicon (Si), and SiQD will allow characterization of all three independent 𝐼𝑚 𝝌 (3) components as determined by the crystallographic point groups of these materials.